Generator



Aug. 4, 1931.

1 M. PERKlNs 1,817,495

GENERATOR Filed Nov. 27. 1928 M7449@ mmm Piuma Aug. 4, '1931 UNITED STATES PATENT ori-ica LAU'RENCII MEBTON PEISIKINS, 0F INDIANA, ABSIGNOB T0 DEMO-REMY CORPORATION, OF DAYTON, QHAIQ, .A COBPQMTION F DELAWARE GENERATOR Application mea November a1, laas. serial ratsam?,

l This invention relates to certain im rovements in variable speed generators, wit specialreference to third brush generators.

The object of this invention is to provide (s means for changing the characteristic curve of the generator with a change in the load.

This is accomplished by providing two sets of windings, one .a shunt winding connected to the third brush and one of the main brushes,

and the other a series winding placed in series with one part of a parallel load, said series winding being disconnected when thel load is reduced, which changes the generator froml that of a substantially compound wound generator to that 'of substantially a shunt wound generator. a f

Another object is to provide a separately excited generator during the time that the armature rotates at such a low speed that the zo terminal voltage is below a lcertain predetermined value. This is accomplished by a relay and a pair of contacts interposed between the enerator and the load and series winding, t e relay exerting an insuilicient force to close the contacts, thus permitting the battery to supply a current through the series windings until the voltage across the main brushes builds up to a predetermined value. Further objects and advantages ofthe pres# ent invention will be a parent from the following description, re erence being had to vthe accompanying drawing, wherein a pref ferred embodiment of one form of the present inventionis clearly shown. i

In the drawing:` The single figure is a schematic diagram of this invention.

The' reference character 10 lndicates ythe with three brushes 11, 12 and 13. Brush 11 is a main brush placed on or near the neutral a d brush 12 is another main brush shifted fr m neutral a distance equal to more than 30 electrical degrees in the direction of rotation ot the armature. The third brush 13 is laced on the opposite neutral froml the main rush. A shunt, field winding nected in serieswith the third ground. By this arrangement of the main 40 armature of the generato` which is provided 1,4 is con#A rush 13 and brushes the generator will generate a substantially uniform voltage over a wide speed range.

Tracing the circuit, the current flows from brush 11 to terminal 15 of the cuteout C, 55

where` it divides, a `small portion flowing through. the high resistance coil 26 to ground. The purpose of coil 26\wi11 be described later. 4The remainder of the current flows through coil 16 through contacts 17 and 18, to arguature 19 to connection or battery terminal 20, where it will divide if switch 24 is closed, some of it flowing through battery 21 to ground, the remainder flowing through the series field 23, through switch 24, through the lighting system 25 on to ground. From this circuit diagram it is clear that when the lighting y switch 24 is closed, the generator operates as a cumulative compound wound generator, while when the switch 24 is open it operates as a shunt wound generator charging the battery. This arrangement of the field windings of the generator provides for an increase of current whenever the lighting switch 24 7| is closed, thereby increasing the output of the generator so that it will simultaneously charge the battery 21 andhfurnish a current to the lighting sgstem 25.

The cutout which comprises the two coils 16 and 26 which are wound upon a common core 27 in such a manner that, the iux set up by eachiof the coils is cumulative or additive as long as the battery is being charged, and compensating or opposing as ,hat soon as the current 'through coil 16 isfrleversed due to a discharge of the batteryfthroughthe generator. As soon 'as the current is reversed through coil 16, spring 30 overcomes the force of the electromagnet upon armature 19. Tension of this springl may adjusted vby a suitable adjusting device Quot shown).

,TWhenever the switch 24 is hissed and ter minai voltage of the generatoi not high g5 `enfringh to close contacts i? i8., the batl ,tei-y., will furnish a current to the series field windings 23 and to the lights 25, or any other suitable load. Thus it is seen that the series windings are separately excited until the im is on neutral, the other main brush is shifted t' more than 30 electrical degrees olf neutral in the direction of rotation of said armature, a third brush on the neutral opposite said first main brush, a shunt field winding connected across the third brush and said other main brush, a series winding connected in series with the load said fields being cumulative and means for disconnectin one of said field windings when reducing't 1e load.

2. A variable speed generator for which the load comprises a battery to be charged and a load connected across the terminals of the main brushes, one of which is on neutral and the other is shifted from neutral in the direction of rotation, a third brush on the neutral opposite the first main brush, a shunt winding across said third brush and said second main brush, a series windin in series with said load and in parallel wit i said batter circuit, means for disconnecting said series winding, thereby changing the generator from a compound wound generator to a shunt Wound generator for charging said battery.

3. A variable speed generator for which the l'oad is connected in parallel to the two main brushes, one of which is on neutral and the other is shifted more than 30 electrical degrees ,from neutral in the direction ofrotation of the armature, a third brush substantially on the neutral opposite the main brush neutral, a shunt field winding connected to the third brush and tothe second mainbrush,

a series winding arranged in serieswith the one of said arallel loads said shunt winding and sai series winding being cumulative, a switch openin the circuit through said load in series wit said series winding, thereby changing the generator from a compound wound generator'to a shunt wound generator.

4. A variable speed generator comprising a rotary armature, two main brushes connected to a load consisting of a battery and of a lamp circuit, one of the main brushes is on neutral and the other main brush vis shifted more than 30 electrical degrees from neutral in the direction of rotation of said armature, a third brush on the. neutral opposite said first main brush, a shunt windin connected to said second main brush and sai third brush, a cut-out connected to said batf tery terminal and 'said first 'main brush, so constructed and arranged as to prevent the discharge of said battery through said armature, a series field winding connected in series with the lamp circuit Iand said first main brush through said cut-out arranged to set up a flux Vcumulative 'to the iux set up by the shunt winding when the lamps are in the circuit and means to disconnect said lam and said series field to thereby change e generator from a compound wound generator to a shunt wound generator.

5. A variable speed generator comprising a rotary armature, two main brushes connected to a load arranged in parallel, one of said main brushes bein placed on neutral, the other being shifted rom neutral, a third brush on the neutral opposite the main brush neutral, a. shunt Winding connected to the,

third brush and one of the main brushes, a series winding in series with one branch of said parallel load, the iux of said series winding and said shunt winding being cumulative, and means to disconnect said series winding,

.thereby changing the generator from a compound wound'generator to a shunt wound generator.

6. A variable speed generator having a plurality of lo'ads one of which is a battery, comprising in combination, a rotary armature, a. pair of main brushes, one placed on neutral and the other shifted from neutral more than 30 electrical `degrees in the direction of rotation of the armature, a third brush on the neutral o posite the main brush neutral, a shunt win mg connected to the main brush shifted from neutral and the third brush, a series winding connected in series with part of the load and in parallel with the battery, and means for operating Said generator as a separately excited generator until vthe terminal voltage across the terminals of the main. brushes attain a predetermined value.

7. A variable speed generator, comprisin in combination, a rotary armature, a pair o main brushes of which one is substantially on neutral and the' other is shifted from neutral, a third brush substantially on the neutral opposite the main brush neutral, a A

shunt field winding, a series field winding, said windings being cumulative, means for separately excitin the generator while starting, relay means or automatically changing the generator from a separately excited to a self-excited compound generator, and means for 'changing the field windings from a compound wound to a shunt wound nerator.

In testimony whereof I hereto a my signature.

LAURENCE MERTON PERKINS. 

